One reason for NOT going to the OTR super singles is that they're still not that common - if you have a tire failure in the middle of nowhere, and call the local tire guy to bring you out a new tire, he might not have one. Which could be a problem.

So, okay, you're going to carry your own spare X-1 or whatever to get around that issue. Can be done, but those things are REALLY HEAVY!! and you might find that getting it out of the bay becomes an unpleasant task, even with the local tire guy assisting. And you'd need yet another spare (if you wanted to feel balanced, Cosmically) for the steer/tag axle...